The present invention relates to a process for the preparation of aromatic carbonyl compound with carbonyl group attached to its aromatic ring. The present invention particularly relates to a process for the preparation of aromatic carbonyl compound with carbonyl group attached to its aromatic ring, by oxidizing with molecular oxygen the methylene or alcoholic group attached to aromatic ring of an aromatic compound, using a polyoxometallate(s) anion exchanged hydrotalcite catalyst.
Background Art
Aromatic carbonyl compounds, such as phenones and aromatic aldehydes are industrially important chemicals, used as organic intermediates for the production pharmaceuticals and perfumery chemicals.
A number of processes are known in the prior art for the preparation of aromatic carbonyl compounds.
Friedel-Crafts Acylation Processes
Both the homogeneous and heterogeneous liquid phase processes based on Friedel-Crafts type reactions for the preparation of aromatic carbonyl compounds, particularly aromatic ketones by acylation of aromatic compounds are known in the prior art.
Friedel-Crafts Acylation Reactions Catalyzed by Homogeneous Catalysts
The Friedel-Crafts type acylation of aromatic compounds by various acylating agents, using homogeneous Lewis acid catalysts, such as AlCl3, BF3, ZnCl2 and other metal chlorides and protonic acid catalysts, such as H2SO4, H3PO4, HF, etc., are well known in the prior art [ref. G. A. Olah, in Friedel-Crafts and related reactions: vol. III, Acylation and related reactions, Wiley-Interscience Publ., New York, 1964].
In a US patent [U.S. Pat. No. 5,476,970 (1995)], Rains et al. disclosed a homogeneous liquid phase process for the acylation of R1R2C6H4 by R3R4C6H3COCl, wherein R1, R2, R3 and R4 are chemical groups, using FeCl3 catalyst at high pressures.
A US patent [U.S. Pat. No. 5,298,664 (1994)] discloses the production of aryl ketones by reaction of aromatic hydrocarbon compounds and aromatic or aliphatic alkyl halides in the presence of anhydride iron (III) chloride.
In French patents [FR 2,768,728 (1999) and FR 2,768,729 (1999)], Baudry et al. disclosed liquid phase homogeneous process for the benzoylation of anisole by benzoyl chloride using rare earth halides or uranyl halide.
In a Japanese patent [JP 08,277,241, A2 (1996)] Kunikata disclosed a liquid phase process for the acylation of phenol by phenyl acetyl chloride using a homogeneous AlCl3 catalyst. A use of AlCl3 as a homogeneous catalyst is also disclosed by Ono for the acylation of toluene with acetyl chloride at high pressure in a Japanese patent [JP 09,059,205, A2 (1997)].
In a very recent Japanese patent [JP 2,000,086,570, A2 (2000)] Shoji et al. have disclosed a homogeneous liquid phase process for the acylation of toluene by acetyl fluoride using HF-BF3 as a catalyst.
The main disadvantages of the Friedel-Crafts acylation processes based on the use of above mentioned homogeneous acid catalysts for the preparation of aromatic ketones are as follows:
1) The separation and recovery of the dissolved acid catalysts from the liquid reaction mixture is difficult.
2) The disposal of the used acid catalysts creates environmental pollution.
3) The homogeneous acid catalysts also pose several other problems such as high toxicity, corrosion, spent acid disposal and use of more than the stoichiometric amount.
Friedel-Crafts Type Acylation Catalyzed by Heterogeneous Solid Catalysts
A few liquid phase processes for the acylation of aromatic compounds by acyl halides using solid catalysts are known in the prior art.
In a Japanese patent [JP 01,089,894, A2 (1995)], Miyata e al. disclosed a liquid phase process for the acylation of toluene with benzoyl chloride using ammionium chloride treated H-beta zeolite catalyst under reflux for 3 h to get para-acylated toluene with 28% yield.
In a recent French patent [FR 2,745,287, A1 (1997)], Barbier et al. disclosed liquid phase acylation of anisole by benzoyl chloride under reflux using neodymium chloride deposited on montmorillonite K-10 clay.
Very recently, in a US patent [U.S. Pat. No. 6,437,191 (2002)], Choudhary et al. disclosed a process for the acylation aromatic compounds by acyl halides to corresponding aryl ketones, using a reusable solid catalyst comprising indium halide.
In the above processes, involving use of solid catalysts, most of the limitations of the homogenous catalyzed Friedel-Crafts acylation processes are eliminated. However these processes also suffer because of the formation of hydrogen halide, which highly corrosive and toxic in nature. Because of the formation of hydrogen halide, these processes are also not environmentally benign. Other limitation of the Friedel-Crafts acylation processes is that the acylating agents used for the acylation of aromatic compounds are quite costly. Hence there is need to develop a better process for the preparation of aromatic carbonyl compounds, which is environmentally more benign and requires low cost feeds, such as that based on the oxidation of aromatic hydrocarbons and alcohols.
Processes for the Preparation of Aromatic Carbonyl Compounds by Oxidation of Aromatic Compounds
A few processes based on the oxidation of aromatic compounds for the preparation of the aromatic carbonyl compounds are also known in the prior art.
In a US patent [U.S. Pat. No. 5,723,676 (1998)] DeWitt, et al have disclosed a process for producing benzophenone by reacting diphenyl methane with manganese dioxide in the presence of a strong acid. This process involves a stoichiometric reaction between diphenyl methane, manganese dioxide and a strong acid, which is highly corrosive, and hence produces a large volume of toxic and corrosive waste.
A US patent [U.S. Pat. No. 4,275,241 (1981)] discloses a process for the preparation of a 3-phenoxy benzaldehyde by contacting 3-phenoxy benzyl alcohol with an aqueous solution of a dichromate and sulphuric acid. This process also involves a stoichiometric reaction between the aromatic alcohol and the dichromate in the presence of sulphuric acid and thereby producing a large volume of toxic and corrosive waste.
A use of molecular oxygen as an oxidizing agent for the oxidation of aromatic compounds in the preparation of aromatic carbonyl compounds is also disclosed in the prior art, as follows.
In a US patent [U.S. Pat. No. 4,366,325 (1982)] Wedemeyer, et al have disclosed a process for the oxidation of 3-phenoxy-benzyl alcohol by oxygen to 3-phenoxy-benzaldehyde using a platinum metal catalyst in aqueous alkali in the presence of lead and/or tellurium and/or bismuth. Because of the aqueous alkali solution, the reaction mixture is corrosive and a corrosive waste is produced in the process.
A US patent [U.S. Pat. No. 4,950,794(1990)] discloses a liquid phase process for the oxidation of ethyl benzene by molecular oxygen to acetophenone and ethyl benzene hydro peroxide in the presence of alkali metal at the elevated temperature. In this process also, alkali metal containing wastewater is produced and also the selectivity for acetophenone is low.
In a US patent [U.S. Pat. No. 4,839,323 (1989)] Goe, et al have disclosed chromium salt bound on an insoluble polymer support as a catalyst for the oxidation with molecular oxygen of ethyl benzene to acetophenone, tetralin to xcex1-tetralone, and 2-methyl-5-ethyl pyridine to 2-methyl-5-acetyl pyridine. However, the leaching of the chromium salt from the polymer is a serious problem (ref. Arends and Sheldon, Applied Catalysis, A: General Vol. 212, Page 175-187, and year 2001). Moreover, in this process, the catalyst shows good activity only at high pressures and temperatures. At the higher temperature and pressure, the oxidation process becomes more hazardous.
Because of limitations of the prior art processes there is great practical need for developing a better process for the preparation of aromatic carbonyl compounds, particularly involving the oxidation of aromatic compounds with molecular oxygen and using reusable solid catalyst having, high stability against leaching, high activity and high selectivity in the oxidation process, and also without using any solvent in the reaction so that the process is environmentally much more benign. This invention was, therefore, made to overcome the drawbacks or limitations of the prior art processes for the preparation of aromatic carbonyl compounds.
The main object of the invention is to provide a liquid phase catalytic process for the preparation of aromatic carbonyl compounds by oxidizing with molecular oxygen the methylene (xe2x80x94CH2) or alcoholic (xe2x80x94CHOHxe2x80x94) group attached to aromatic ring of aromatic compounds to a carbonyl group (xe2x80x94COxe2x80x94), using a solid catalyst.
An object of the invention is to provide a liquid phase oxidation process for the preparation of aromatic carbonyl compounds, which can be operated without any solvent and does not produced any corrosive and/or toxic by-product(s) and, hence, is environmentally benign.
Yet another object of this invention is to provide a catalytic oxidation process for the preparation of aromatic carbonyl compounds, which can be operated even at or close atmospheric pressure and, hence, is less hazardous.
The present invention relates to a process for the preparation of aromatic carbonyl compound with carbonyl group attached to its aromatic ring. The present invention particularly relates to a process for the preparation of aromatic carbonyl compound with carbonyl group attached to its aromatic ring, by oxidizing with molecular oxygen the methylene or alcoholic group attached to aromatic ring of an aromatic compound, using a polyoxometallate(s) anion exchanged hydrotalcite catalyst.